The specific purpose of this program is to elucidate the structure of the carbohydrate component of porcine intimal glycoprotein named "lipolipin" (Lipoprotein Lipase Inhibitor) and to explore the mechanism by which lipolipin inhibits the lipolytic activity of lipoprotein lipase. Porcine lipolipin (MW 72,000) does not contain subunits, its N-terminal amino group is not free and its C-terminal amino acid is serine. It does not contain an alkali-labile linkage. A prediction has been made as to the general features of its carbohydrate moiety. Porcine lipolipin is an inhibitor of purified lipoprotein lipase from bovine milk. We wish to study further the following aspects: (1) The sequence and linkages of sugars and the carbohydrate-peptide linkage; (2) The kinetics of in vitro inhibition of purified lipoproteinlipase by native and modified lipolipin (after selective cleavage of sugars) employing various artificial and physiological triglyceride substrates; and (3) The feasibility of developing an immunological technique for the localization of lipolipin. The structure of the carbohydrate component will be determined using both the native molecule and the glycopeptides derived therefrom. Enzymatic as well as chemical techniques (e.g., specific glycosidases, oxidation with periodate) will be used. The kinetics of inhibition will be studied employing purified lipoprotein lipase preparations from various sources (e.g., bovine milk, post-heparin plasma, adipose tissue) as the enzyme source. Artificial triglyceride emulsions (activated by serum or apo C-II) and lipoproteins (chylomicrons and very low density lipoprotein) will be used as substrates. We have evidence that lipolipin is antigenic. Anti-lipolipin will be purified so as to localize the antigen in tissues. The potential significance of this research is in the area of regulation and control of lipid transport.